Pypy: Another Version of Py Eli Biham, Jennifer Seberry Department - PowerPoint PPT Presentation

Pypy: Another Version of Py Eli Biham, Jennifer Seberry Department of Computer Science Technion, Haifa 32000, Israel March 16, 2006 c � Eli Biham - March 16, 2006 1 RUMP session, FSE 2006, Graz, Austria

Py 1. Stream cipher 2. Submitted to eStream 3. Very fast: 2.85 cycles/byte on Pentium (RC4 takes 7). 4. It uses rotating arrays, and ideas similar to RC4 5. Outputs two 32-bit words at a time 6. Has another version Py6 c � Eli Biham - March 16, 2006 2 RUMP session, FSE 2006, Graz, Austria

Pypy (Pronounced Roopy or Rupee) 1. The original version of Py 2. Provides extra security over Py, for those applications for which distin- guishing attacks that require more than 2 64 bytes of streams (thus from many streams with many keys) is not secure enough 3. Runs at speeds of about 4–4.5 cycles/byte 4. Outputs only the first word of every two words of Py 5. Identical to Py in any other sense 6. We will ask eStream to consider Pypy, in addition to the current candi- dates Py and Py6 c � Eli Biham - March 16, 2006 3 RUMP session, FSE 2006, Graz, Austria

Pseudocode of Pypy 1. Use Py 2. Setup the key and IV as in Py 3. Run Py with twice the size of the required output 4. Select every second word of the generated key stream (starting with the first word) c � Eli Biham - March 16, 2006 4 RUMP session, FSE 2006, Graz, Austria

A Pypy in the Hand is Worth more than in the Bush c � Eli Biham - March 16, 2006 5 RUMP session, FSE 2006, Graz, Austria

The End c � Eli Biham - March 16, 2006 6 The End